Silicon controlled rectifier actuated liquid gas filler



A. A. THIELE Dec. 7, 1965 SILICON CONTROLLED RECTIFIER AGTUATED LIQUIDGAS FILLER 2 Sheets-Sheet 1 Filed Sept. 26, 1963 CONTROLLER 2.2

INVENTOR Alfred A. Thiele w &

FIG.3.

ATTORNEYS Dec. 7, 1965 A. A. THIELE 3,222,578

SILICON CONTROLLED RECTIFIER ACTUATED LIQUID GAS FILLER Filed Sept. 26,1963 2 Sheets-Sheet 2 FIG.4.

INVENTOR Alfred A.Thiele BY M ATTORNEYS United States Patent 3,222,578SILICON CONTROLLED RECHFIER ACTUATED LIQUID GAS FILLER Alfred AlmstedtThiele, Box 307C, Graduate House, 305 Memorial Drive, Cambridge, Mass.Filed Sept. 26, 1963, Ser. No. 311,902 11 Claims. ((31. 317--148.5)

This invention relates to automatic filler systems for liquid gases andthe like, such as liquid nitrogen, and more particularly to intermittentautomatic filler systems which regulate the level of liquid gas in aparticular receptacle.

It is an object of this invention to provide a novel intermittentautomatic filler system for liquid gas and the like.

It is another object of this invention to provide a novel intermittentautomatic filler system for liquid gas and the like characterized bysmall size and simplicity.

Another object of this invention is to provide a novel intermittentautomatic filler for liquid gas and the like which maintains the levelof liquid gas in a receptacle between predetermined limits.

Still another object of this invention is to provide a novelintermittent automatic filler for liquid gas and the like having a novelsilicon controlled rectifier circuit and a filler valve controlledthereby.

These and other objects of the invention will become more fully apparentwith reference to the following specification and drawings which relateto several preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a schematic of a liquid gas filler system of the presentinvention;

FIGURE 2 is a circuit diagram of a first embodiment of the invention;

FIGURE 3 is a circuit diagram of a second embodiment of the invention;and

FIGURE 4 is a circuit diagram of a commercial embodiment of theinvention.

Referring in detail to the drawings, and more particularly to FIGURE 1,the filler system is shown as generally comprising a first or storagedewar iii and a second or supplied dewar 12 interconnected by a transfertube 14, the latter extending substantially to the bottom of the firstdewar It) and slightly into the second dewar 12.

Liquid gas 16, such as liquid nitrogen is generally shown in the seconddewar i2 as having a level I8 which level is to be regulated under thepresent invention.

Sensor means for detecting upper and lower limits of the liquid level 18is provided in the form of an upper limit thermistor T and a lower limitthermistor T connected by circuit means 20 with an electronic controllermeans 22.

The controller means 22 has an output comprising driving means 24 for acontrol valve 26.

The control valve 26 is connected in a pneumatic line 28 which isconnected at one end to a source 3%) of dry air or nitrogen and at theother end to the inlet 32 of the storage dewar It in the neck portion 34thereof. The inlet 32 is suitably sealed around the pneumatic line 28and the transfer tube 1.4.

The control valve 26 is a two-way valve in that it is controllable toeither connect the storage dewar lid with the pneumatic source or ventthe storage dewar it to atmosphere.

Referring now to FIGURE 2, one embodiment of the electronic controllermeans 22 will now be described in detail.

An alternating current source 36 is connected at one side to a commonground lead 38 and at the other side 3,222,573 Patented Dec. 7, 1965 toa common lead 40 via a first half-wave rectifier diode D1.

A first branch circuit is connected between common leads 38 and 4dcomprising a second diode D2 extending from anode terminal 42 at theline 40 to a first junction point 44 comprising its cathode terminal,and a first resistor R11 and the upper limit thermistor T connected inseries from the junction point 44 to a terminal 46 at the ground line38.

A second branch circuit is connected between common leads 38 and 44comprising a silicon controlled rectifier 48, hereinafter referred to asSCR iii, connected via its cathode terminal St) to a terminal 52 on theline 40 and connected at its anode terminal 54 to a second junctionpoint 56, and a solenoid circuit 58 connected between the junction point56 and a terminal 60 at the ground line 38.

The solenoid circuit 58 comprises a first parallel branch having asecond resistor R2 connected at the second junction point So to theanode side of a third diode D3 which is connected at its cathode to theterminal 60; and a second parallel branch having a third resistor R3connected from the second junction point 56 to one side of a solenoidwinding S which, in turn, is connected at its other end to the terminal6%. The solenoid winding S comprises the control winding for the controlvalve 26 which is of the solenoid type.

A third branch circuit is connected across the common lines 38 and 4dand comprises a parallel branch biasing circuit d2 connected at one endto a terminal 64 on the common line 44b and at its other end to thelower limit thermistor T the latter being connected to the common groundline 38 via the terminal 60 of the solenoid circuit.

The biasing circuit 62 comprises a fourth resistor R4 in parallel with avoltage divider having fifth and sixth series resistors R5 and R6,respectively, with a junction therebetween comprising the gate terminal66 of the SCR48.

The first and second branch circuits are interconnected at therespective junction points 44 and 56 via a seventh resistor R7 extendingfrom the junction point 44 to the anode of a fourth diode D4, the latterbeing connected at its cathode to the junction point 56.

Referring now to FIGURE 3, another embodiment of the invention is shownwhich includes many like parts to the embodiment of FIGURE 2, thesebeing indicated by like numerals.

In this embodiment, the second diode D2 in the first branch circuit isshunted by an eighth resistor R8. The rest of the first branch circuitis identical to that of the embodiment of FIGURE 2.

The solenoid circuit 58 of FIGURE 2 is replaced in FIGURE 3 by asolenoid circuit 58' comprising the third diode D3 and second resistorR2 in exchanged positions in the first parallel branch thereof and asecond parallel branch consisting solely of the solenoid winding S. Acommon terminal 68 is provided for the second resistor R2 and thesolenoid winding S and is connected via a ninth resistor R9 to theterminal 60 on the common ground line The SCR iti and the third branchcircuit are identical to the corresponding elements of FIGURE 2.However, the seventh resistor R7 and the fourth diode D4 of FIGURE 2 arenot present in FIGURE 3.

Referring now to FIGURE 4, a commercial embodiment of the invention isshown as including a power plug 70 and an on-oif switch 72 connectingthe power plug 70 with the common lines 33 and ed.

An on-oif indicator means 74 comprising a neon bulb 75 and seriesresistor 78 connected as a branch circuit across the common lines 38 and40 adjacent the switch 72.

The remainder of the circuit i substantially identical 3 with that ofFIGURE 3 with the exception that a switch 84) is provided in shunt withthe lower limit thermistor T and the first resistor R1 has been removed.

OPERATION Referring now to FIGURES 1 and 2, the operation of theembodiment of FIGURE 2 will now be described.

Assuming that the fluid level 18 has fallen below the lower limitthermistor T the lower thermistor T will no longer be cooled by theliquid gas 16. Since the first diode D1 passes negative half-cycles ofcurrent from the source 36, a current path through lower thermistor Tvia the fourth resistor R4 and common lines 33 and 44) is established.This causes the lower thermistor T to heat up by the energy dissipatedtherein and cause a decrease in the resistance thereof. The current thusincreases, the temperature further increases and the resistance furtherdecreases comprising a runaway action in the lower thermistor T Thevalues of the fifth and sixth resistors R5 and R6 are chosen so thatthey present the proper firing potential to the gate terminal 66 of theSCRdS, derived from the voltage drop across the fourth resistor R4, whenthe lower thermistor T is out of the fluid 16 and the above-definedrunaway action has commenced.

When the SCR48 fires, a current path is created through the solenoidwinding S via common line 33, terminal 60, third resistor R3, whichlimits the current in the winding S, junction 56, SCR48, terminal 52 andcommon line 4%). During positive half cycles at the source 36, thesecond resistor R2 and third diode D3 provide a path for the current inthe inductive winding S. A a result, the solenoid valve 26 is actuatedto connect the pressure source 30, via pneumatic line 28, with thestorage dewar 19. This forces liquid gas in the storage dewar 16 intothe controlled dewar 12 via the transfer tube 14.

The firing of the SCRdS results in a heating of the upper thermistor Tvia the current path comprising the SCRdS, fourth diode D4, seventhresistor R7 and first resistor R1 between the common lines 38 and 4th.

The fluid level 18 is now rising and the fluid 16 envelops the lowerthermistor T which cools to low conductivity and thus prevents thefiring potential from being provided at the gate terminal 66.

However, because of the inductive memory or storage characteristics ofthe winding S, the voltage thus provided across the limiting thirdresistor R3 drives a current through the upper thermistor T and itsabove-defined current path to maintain the SCR48 on.

The fluid level 18 continues to rise until the fluid 16 envelops theupper thermistor T causing the latter to cool. A resulting rise inresistance in the upper thermistor T causes the holding current toeffectively cut off below the value needed to sustain the SCR ES in anon condition. Thus the SCR48 cuts off, de-energizing the solenoidwinding S and causing the two-way solenoid valve 26 to vent the storagedewar 10 to atmosphere via the pneumatic line 28. This removes thepressure differential which causes the liquid therein to pass throughthe transfer tube 14 and thus the control cycle is complete. The cycledoes not repeat until the fluid level 18 falls below the lowerthermistor T In the embodiment of FIGURE 3, the initiation of thefilling cycle is identical with that of the embodiment of FIGURE 2.

However, because of the second diode D2 and the memory characteristic ofthe winding S, the SCRd? will be held on during positive half cycleswhen the upper thermistor T is out of the fluid 16 and the lowerthermistor T is immersed in the fluid 116. As soon as the upperthermistor T becomes immersed its impedance substantially increases suchthat on the next occurring positive half cycle of the source 36 theSCR48 is cut off.

Referring now to FIGURE 4, the operation is identical to that of FIGURE3. However, certain variations may be effected by means of the powerSWitCh 72 and the shunt switch 89.

By opening the power switch 72 during a filling cycle the fluid level 1%may be selectively positioned, since this causes the SCR i to cut off byremoving the energy supply thereto.

Additionally, even though the lower thermistor T is submerged in thefluid 16, the level 18 may be changed selectively by closing the shuntswitch 80, shorting out the lower thermistor T and initiating thefilling cycle.

The cycle may be permitted to terminate normally or the power switch 72may subsequently be opened to selectively position the fluid level 18.

The on-off indicator is energized by the closing of the power switch 72,the resistor 78 acting to limit the current through the neon lamp 76.

A table of relative values for the circuit parameters of FIGURE 3 is asfollows:

Elements: Value or type SCR l-S s 2N2326. S General ControlsK273DA4322BDE.

T and T Carborundum T-l. D1, D2, D3 IN441B.

R2 390 ohms 1 Watt. R4 7.5K 1 watt.

R5 1K /2 watt.

R6 43K k watt.

R3 7.5K 1 watt.

R9 250 ohms 10 watt.

As can be seen from the foregoing specification and drawings, thisinvention provides a new and novel liquid gas filling system with anovel silicon controlled rectifier control circuit utilizing the thermalcon-ductivity characteristics of a pair of thermistors to effect upperand lower limits of operation and further utilizing the inherent memorycharacteristics of a controlled means to effect a holding on of thesilicon controlled rectifier bet-ween said limits of operation.

It is to be understood that the several embodiments of the inventionshown and described herein are for the purpose of example only and arenot intended to limit the scope of the appended claims.

What is claimed is:

1. For use in a liquid gas filler system including a solenoid fillervalve, having a solenoid winding therein, for effecting a transfer ofliquid gas from a first container to maintm'n a fluid level in saidsecond container between preselected upper and lower limits, a controlcircuit for said solenoid valve selectively energizing said solenoidwinding in response to said fluid level comprising a power sourcesupplying half-wave rectified power pulses to said circuit; first andsecond common power lines connected one on either side of said source; afirst branch circuit across said power lines including first thermistormeans adapted to be submerged in said liquid gas at said upper limitproviding a maximum electrical resistance at said upper limit and aminimum electrical resistance at lesser fluid levels; a second branchcircuit across said power lines including second thermistor meansadapted to be submerged in said liquid gas above said lower limitproviding a maximum resistance in response to fluid levels greater thansaid lower limit and a minimum resistance at or below said lower limit,and biasing means in series with said second thermistor means; a thirdbranch circuit across said power lines including a silicon controlledrectifier, having an anode-cathode current path and a gate terminal, andsaid solenoid winding f said valve connected in series with saidanode-cathode path; first circuit means connecting said gate terminalwith said biasing means; and second circuit means connecting said firstthermistor means in series with said anode-cathode current path of saidcontrolled rectifier in the interim between said half-wave power pulses;said first circuit means, said gate terminal, said biasing means andsaid second thermistor means rendering said controlled rectifierconductive and effecting energization of said solenoid winding inresponse to a fluid level less than said lower limit; said secondcircuit means, said first thermistor means and said solenoid windingcooperating to apply a holding current to said anode-cathode path andmaintain the previously energized controlled rectifier continuouslyconductive when said fluid level is between said lower and upper limits.

2. The invention defined in claim 1, wherein said first branch circuitfurther includes diode means and resistance means connected at a firstjunction and in series with said first thermistor and said third branchcircuit includes a second junction between said solenoid winding andsaid controlled rectifier, and said second circuit means comprisingunidirectional conducting means interconnecting said first and secondjunctions.

3. The invention defined in claim 1, wherein said third branch circuitfurther includes resistance means in series with said solenoid windingand means including diode means in shunt with said resistance means andsolenoid winding.

4. The invention defined in claim 1, wherein said third branch circuitfurther includes means including diode means in shunt with said solenoidwinding and resistance means mutually in series therewith.

5. The invention defined in claim 1, wherein said control circuitfurther includes first switch means in shunt with said second thermistorand second switch means interconnecting said common lines and saidsource.

6. The invention defined in claim 1, wherein said first branch circuitfurther includes diode means.

7. For use in a means for maintaining the level of a liquid between anupper and a lower limit in a container, said means including storagemeans for said liquid and motive means for transferring said liquid fromsaid storage means to said container, a control circuit for said motivemeans comprising a solenoid winding adapted to effect actuation of thesaid motive means; first thermistor means adapted to be submerged insaid liquid at the upper limit thereof; second thermistor means adaptedto be submerged in said liquid above said lower limit thereof; a powersource; a silicon controlled rectifier means in circuit with saidsolenoid winding and said power source selectively controlling the flowof power from said power source through said Winding; bias circiut meansconnected across said power source controlled by and including saidsecond thermistor means, rendering said controlled rectifier meansconductive and energizing said winding when the level of the said liquidis below said lower limit; and holding circuit means including saidfirst thermsitor and said solenoid winding maintaining said controlledrectifier means conductve once the latter has been rendered conductiveby said bias means and until the said liquid reaches its upper level.

8. The invention defined in claim 7, wherein said bias means furtherincludes switch means selectively shunting said second thermistor tofire said controlled rectifier means when said fluid level is above saidlower limit.

9. In a means for maintaining the level of a liquid in a containerbetween upper and lower limits including solenoid means for selectivelyeffecting a supply of liquid to said container, a control circuit forsaid solenoid means comprising a solenoid winding for said solenoidmeans, a power source, a first thermistor positioned at said upper limitand a second thermistor positioned at said lower limit in saidcontainer, both of said thermistors being connected across said source,silicon controlled rectifier means controlling said solenoid means andconnected in circuit with said solenoid winding across said powersource, bias means controlled by and including said second thermistor,in circuit with said power source and said controlled rectifier meansfiring said controlled rectifier means when the level of said liquid isbelow said lower limit, and holding means controlled by and includingsaid first thermistor and said solenoid winding maintaining saidcontrolled rectifier means on when the level of said liquid is betweensaid upper and lower limits, subsequent to the firing of said controlledrectifier means.

10. The invention defined in claim 9, wherein said bias means furtherincludes switch means selectively shunting said second thermistor tofire said controlled rectifier means when said fluid level is above saidlower limit.

11. The invention defined in claim 1, wherein said second circuit meanscomprises unidirectional conducting means in series with said firstthermistor means and said anode-cathode path of said silicon controlledrectifier and in shunt with a portion of said first branch circuit.

References Cited by the Examiner UNITED STATES PATENTS 3,049,887 8/1962Sharp et a1 62-51 X 3,050,611 8/ 1962 Kamide. 3,084,708 4/1963 Herrero137392 ISADOR WEIL, Primary Examiner.

ROBERT A. OLEARY, Examiner.

7. FOR USE IN A MEANS FOR MAINTAINING THE LEVEL OF A LIQUID BETWEEN ANUPPER AND A LOWER LIMIT IN A CONTAINER, SAID MEANS INCLUDING STORAGEMANS FOR SAID LIQUID AND MOTIVE MEANS FOR TRANSFERRING SAID LIQUID FROMSAID STORAGE MEANS TO SAID CONTAINER, A CONTROL CIRCUIT FOR SAID MOTIVEMEANS COMPRISING A SOLENOID WINDING ADAPTED TO EFFECT ACTUATION OF THESAID MOTIVE MEANS; FIRST THERMISTOR MEANS ADAPTED TO BE SUBMERGED INSAID LIQUID AT THE UPPER LIMIT THEREOF; SECOND THERMISTOR MEANS ADAPTEDTO BE SUBMERGED IN SAID LIQUID ABOVE SAID LOWER LIMIT THEREOF; A POWERSOURCE; A SILICON CONTROLLED RECTIFIER MEANS IN CIRCUIT WITH SAIDSOLENOID WINDING AND SAID POWER SOURCE SELECTIVELY CONTROLLING THE FLOWOF POWER FROM SAID POWER SOURCE THROUGH SAID WINDING; BIAS CIRCUIT MEANSCONNECTED ACROSS SAID POWER SOURCE CONTROLLED BY AND INCLUDING SAIDSECOND THERMISTOR MEANS, RENDERING SAID CONTROLLED RECTIFIER MEANSCONDUCTIVE AND ENERGIZING SAID WINDING WHEN THE LEVEL OF THE SAID LIQUIDIS BELOW SAID LOWER LIMIT; AND HOLDING CIRCUIT MEANS INCLUDING SAIDFIRST THERMSITOR AND SAID SOLENOID WINDING MAINTAINING SAID CONTROLLEDRECTIFIER MEANS CONDUCTIVE ONCE THE LATTER HAS BEEN RENDERED CONDUCTIVEBY SAID BIAS MEANS AND UNTIL THE SAID LIQUID REACHES ITS UPPER LEVEL.